1. Technical Field
The present invention relates to a liquid developer and an image forming apparatus.
2. Related Art
As a developer to be used for developing an electrostatic latent image formed on a latent image carrying member, a liquid developer obtained by dispersing a toner constituted by a material containing a colorant such as a pigment and a binder resin in an electrically insulating carrier liquid (insulating liquid) is known.
As the binder resin to be used in toner particles constituting such a liquid developer, a polyester resin is widely used in general. The polyester resin has a high transparency and when it is used as a binder resin, it exhibits characteristics that a color developing property of the resulting image is good and a high fixing property can be obtained.
As the liquid developer, a negatively charged liquid developer and a positively charged liquid developer can be exemplified. In the case of using a negatively charged liquid developer, there were problems that ozone was generated in an image forming apparatus when an image was formed, resulting in causing an environmental problem or an adverse effect on peripheral units in the image forming apparatus, etc.
Therefore, recently, development of a method for forming an image using a positively charged liquid developer with which image formation can be performed by reducing a produced amount of a discharge product such as ozone has been advanced (see, for example, JP-A-2002-214849).
In the positively charged liquid developer described in JP-A-2002-214849, toner particles are positively charged by adding a charge control agent.
However, a polyester resin which has been used in toner particles generally has a high negative charging property, therefore, it was difficult to apply a polyester resin to positively charged toner particles (liquid developer). Further, it is conceivable that related toner particles using a polyester resin as a binder resin are positively charged by adding a charge control agent to the toner particles, however, it was difficult to obtain a sufficient charge amount.
Further, to a liquid developer, a dispersant is added for improving the dispersibility of toner particles. However, in general, when a dispersant was added, there was a problem that a charging characteristic of the liquid developer was decreased.